This invention relates to an attachment device for attaching a lifting sling to a hoist. The lifting sling is used to lift and support a person, such as an invalid or patient.
A lifting sling is usually attached to a hoist by providing the sling with a number of elongate flexible connecting elements, which are each at one end secured to a flexible sheet material from which the sling is made, and at another end provided with an attachment device for engagement with an attachment formation on the hoist. The flexible connecting elements may be flexible strap elements made of a woven textile tape, or length of webbing, of sufficient strength to carry a load to which the sling is likely to be subjected in use. There may be two such connecting elements and attachment devices, one at each side of the sling in a region thereof which is in the vicinity of the shoulders of a person being supported by the sling in use, and further two such connecting elements and attachment devices may be provided at respective parts of the sling that lie in the lower torso or upper leg region of a person supported by the sling, in use.
It is known that each of the attachment formations on the hoist (usually on a load-carrying cradle carried by the hoist) can comprise a headed stud, and each attachment device engageable therewith can comprise a keyhole slot or the like, having a first portion through which the head of the stud can pass and a second portion which can be entered by a body part of the headed stud after the head has been passed through the first portion, but through which the head of the stud cannot pass. When a part of the weight of a person is being carried by such an attachment device, the body of the headed stud is held in the second portion of the opening so that the attachment device cannot come off the stud. It has also been proposed that various locking or latching devices cannot be provided in association with such an attachment device, to provide greater security against unintentional disengagement of the attachment device from the headed stud.
What is needed is an improved form of attachment device for engagement with an attachment formation in the form of a headed stud, which not only provides a high degree of resistance to unintentional disengagement but also provides a clearly-visible indication as to when it is correctly engaged and thus, offers the maximum resistance to unintentional disconnection.